Film: "Ajab Prem Ki Ghazab Kahani"; Cast: Ranbir Kapoor, Katrina Kaif; Director: Rajkumar Santoshi; Rating: ***

If you've ever wondered what on earth is on-screen chemistry, here's your one-stop all-purpose encyclopaedia on celluloid magic.

Fasten your seat belts as veteran filmmaker Rajkumar Santoshi pulls out all stops to do a wacky, goofy weightless comedy of characters who walk in and out of frames, leaving behind fumes of old-fashioned comic acts. 

"Ajab Prem Ki Ghazab Kahani" is a trapeze down the familiar romantic lane. The starting point seems to be "Saawariya". A loud interpretation of Ranbir Kapoor's character in Sanjay Leela Bhansali's on-screen opera, Prem in "Ajab Prem'..." adores the girl next door Jenny. 

But she loves someone else. No it's not Salman Khan, though in a tongue-in-cheek homage to tabloid realism, Katrina meets her idol Salman, who drawls to the roadside Romeo Ranbir: "You're behaving as if you're making my girlfriend your own."

As in "Saawariya", "Bachna Ae Haseeno" and the recent "Wake Up Sid", a major part of the narrative becomes a showcase for Ranbir's skills as an all-purpose actor who can pull out any emotional response to the most sterile dramatic stimuli. 

In sequence after sequence, written to spotlight the young actor's virtuosity, Ranbir rises above the material given to him with gusto.

Even while mouthing corny, sappy dialogues about serving 'moong-dal ke pakode' to his beloved or plucking stars from the sky for her, Ranbir makes the trite seem just right. 

His phenomenal talent gets radiant support from Katrina Kaif, who gets better with every film. As the waif with a face so vulnerable and imploring, Katrina is at once haughty, feisty and flirtatious. She's every man's dream-come-true, so why not Prem's?

Would "Ajab Prem..." have worked as such a sleek showreel for the besotted-boy-meets-absent minded-girl's tale without the same lead actors? The answer is an emphatic no. 

The noticeably over-done comic situations include a cartel of goofy goons who pop up towards the end to join the party. In one laboured sequence of comicality, Ranbir has to wear Katrina's bodice and pretend he wears such clothes comfortably to avoid exposing Katrina's concealment in his home.

The above scene is among the many that Ranbir and Katrina essay with ease that makes "Ajab Prem..." a watchable potpourri of parodies.

This is a rare film that jumps over all the hurdles of cliched plotting and corny dialogues on the sheer strength of its protagonists' charm and grace. The film wears a bright, sunny look. The location is an obviously papier-mache town filled with a benign bonhomie that doesn't go beyond surface-level romanticism.

And yet, several individual sequences come alive to convey a sparkling potency. Check out the sequences where Ranbir and Katrina stammer under emotional stress both individually and separately. 

Is there a better star-pair than Ranbir and Katrina in recent times? Maybe there is...But who cares. This one just makes you want to cuddle them.